1. Field of the Invention
The present invention relates generally to the fields of optometry, opthalmology and pathologies of the eye. More specifically, the present invention provides a method and system for screening individuals at risk for or having macular degenerative diseases and related central retinal and peripheral retinal conditions to optimize therapeutic interventions.
2. Description of the Related Art
Recent estimates indicate that approximately 8 million Americans have reduced vision as the result of AMD. The prevalence of AMD increases dramatically with age, from approximately 12% of seventy year olds to nearly 25% of people aged 80 or older. Consequently, as the population of the United States ages the total number of afflicted individuals is certain to increase. The vision loss that occurs as the result of AMD has severe adverse consequences for many essential day-to-day activities, such as reading, face recognition, and driving.
Two main forms of age related macular degeneration (AMD) are distinguished clinically, i.e., the “dry,” atrophic form and the more devastating exudative, or “wet,” form. Until a few years ago, exudative AMD was relatively untreatable. However, newly developed medical treatments can slow or even partly restore vision loss to a limited degree (1-2). These treatments require the injection into the vitreous of anti-VEGF agents that retard the growth of new, sub-retinal vessels, which leak fluid into the macula and lead eventually to macular scarring. Because intravitreal injections are uncomfortable for patients, costly, and include a risk of serious complications, substantial current clinical research focuses on determining the appropriate treatment interval and total duration of these injections (3-4). Ideally, the timing of injections should be determined on a patient-by-patient basis with the maximum temporal interval that prevents the accumulation of retinal fluid.
For many years, the Amsler grid was used as a subjective home-monitoring test to alert patients to the possible onset of macular changes. However, the Amsler grid has been shown to be relatively insensitive, as a high proportion of patients with documented visual field losses nevertheless report that the Amsler grid appears to be complete and undistorted (5-7). This is accounted for by perceptual filling-in, whereby the visual system uses information from intact areas of the retina that surround a region of visual field loss to generate a complete and undistorted perception of regular patterns or edges that impinge on the scotoma (8-9). Recently, the PreView PHP was reported to identify perceptual changes associated with the development of choroidal neovascularization in patients with intermediate AMD more accurately than the Amsler grid (10-11). However, this instrument is intended primarily for in-office use by eye-care practitioners or their technical staff.
Thus, there is a recognized need in the art for subject friendly, improved low cost methods of screening for or monitoring the progression of macular degenerative diseases. Specifically, the prior art is deficient in methods of using orientation discrimination thresholds in determining if a subject is at risk for a macular degenerative disease or to monitor the progression thereof in subjects undergoing treatment. The present invention fulfills this long-standing need and desire in the art.